Can anyone recommend a replacement for OPA2134 (hence, dual - browndogs won't fit my unit) that has excellent PSRR? My PSU is a wall wart (says regulated, but I doubt it), so trying to hunt down an opamp with the best PSRR.

Additionally, the headphone amp this is for uses a circuit which biases the output heavily into class A - any chips out there which would benefit from this?

Best PSRR I know of is National's LME49990, though I suspect it'll be some time before a dual version's available. The LME49720/49860 offer a slight gain over the 2134 (but their main advantage is they sound a bit more precise, probably due to the higher GBP). If you want more rejection you'd be better off throwing together a basic 7815/7915 type supply; that'll give you 60-80dB versus the 10-30dB from an op amp upgrade. Chips are cheaper too. Seeing as the 2134s are ~110dB I'd be surprised if PSRR is really an issue; have you measured the ripple or checked for bad bypass caps?

Can anyone recommend a replacement for OPA2134 (hence, dual - browndogs won't fit my unit) that has excellent PSRR? My PSU is a wall wart (says regulated, but I doubt it), so trying to hunt down an opamp with the best PSRR.

With typical decoupling arrangements, your performance is probably not going to be PSRR limited. Rather it will most likely be limited by power supply hash coming down onto the signal ground through the decoupling capacitors. Better to regulate the wall wart (relatively easy) or rejig the grounding (more difficult).

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Just add some Bypass caps close to the IC Pins , It will filter out some of the PSU noise ...... Or built a well filtered Regulated supply and drop the wall mart ....

So long as those caps are between the rails, it could be a good idea. If you tie them to the signal ground, all that happens is you dump power supply rubbish on your ground. The second option is sounder.

__________________“A new scientific truth does not triumph by convincing its opponents ... but rather because its opponents eventually die, and a new generation grows up that is familiar with it.” - Max Planck

Thanks people - that's a great start. I'm going to build a better PSU. My headamp pcb already has 470uF caps on it, so you are probably correct simply swapping the opamp may not make too much differece. I notice that OPA2134 gives a nice, well defined bass, but the top end is a little shrill and not as tightly defined as the bass - how would the LME49990 compare with this?

Can anyone recommend a replacement for OPA2134 (hence, dual - browndogs won't fit my unit) that has excellent PSRR? My PSU is a wall wart (says regulated, but I doubt it), so trying to hunt down an opamp with the best PSRR.

So measure the output off and on load to see what the regulation is.
Scope the output under load to see what the ripple/noise is.

Thanks Mooly & AndrewT -
(1) How to I measure the regulation with a multimeter (bear in mind I'm a newbie).
(2) I've attached the circuit for one channel - C3 is 470uF because I'm using a wall wart - does this clarify anything (unsure whether this cap is 'decoupling' anything).